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GE Fr9E Units Combined Cycle Operating with High Back Pressure

10/27/2016 6:46 AM

The site configuration is 03 Fr9001E Units + 03 HRSG + 01(common) Steam Turbine. The HRSGs were a poor design and resulted in the GTs running with continous high exhaust pressure ( 410 ~ 420 mm H2O, which is close/above the alarm limit), while the situation as expected gets worse during winters for 1~2 months ( 445 ~460 mm H2O). The trip is set at 520 mm H2O. The Vibration levels and axial thrust have remained within normal limits during this time and the exhaust section inspection did not reveal anything unusual. Going forward, there is a plan to install inlet chilling on the units which will result in constant very high back pressure similar to winter conditions. We are contacting the OEM, but will appreciate if someone can share similar experience and knowledge with regards to high back pressure and mechancial integrity of the units. Thanks.

Re: GE Fr9E Units Combined Cycle Operating with High Back Pressure

10/30/2016 5:36 PM

So let's see, you have a situation that worsens during two months of the year, and you want to correct it by artificially forcing the condition to exist throughout the year. Which OEM are you contacting, the HRSG's, GE, or the overall plant designer?

Personally I'd be pursuing the designer of the plant, unless the HRSG was an afterthought/add-on to an existing open cycle plant. In any case I would go with the party that suggests reducing the back-pressure by either removing some of the existing HRSG surface area, or adding a parallel exhaust path with another HRSG in it. The challenge of course will be to balance the exhaust flow to maintain the desired steam conditions. Good luck to you.